Electric device including an electric fan and a control unit for controlling the electric fan

ABSTRACT

An electric device has a casing with an air-inlet and an air-outlet, a main unit disposed inside the casing, a first temperature sensor for detecting the temperature inside the casing, a second temperature sensor for detecting the temperature outside the casing, an electric fan, and a control unit. The control unit rotates the electric fan at the time of the low-temperature startup such that the temperature detected by the first temperature sensor is lower than a preset first threshold value, while the temperature detected by the second temperature sensor is higher than the temperature detected by the first temperature sensor.

INCORPORATION BY REFERENCE

The present application claims priority from Japanese Patent ApplicationNo. 2011-39246, filed on Feb. 25, 2011 in Japan, the disclosure of whichis incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to electric devices and, in particular, toa method of starting up electric devices in low-temperature environment.

BACKGROUND ART

Generally, there is a range of guaranteed operating temperature forelectric devices, and it is possible that electric devices do notoperate normally in environments out of the range. For example, in thecase of electric devices with the guaranteed operating temperature from−5° C. to 40° C., continuous utilization in a high-temperature rangeover 40° C. for a long time may result in faulty or malfunction.Further, when starting up the electric devices at low-temperatures below−5° C., problems such as damage or deterioration of the components arelikely to occur due to rapid change in temperature right after thestartup.

Therefore, electric devices are provided with a cooling mechanism suchas cooling fans and the like as a measure against high temperature.Further, as a measure against low temperature, there are electricdevices equipped with a mechanism for preventing rapid temperature riseright after the startup.

For example, the electric device disclosed in the following PatentDocument 1 has a cooling fan and a fan control device with a temperaturesensor as the measure against high temperature. The fan control devicewith a temperature sensor adjusts the temperature inside the device bycontrolling the starting and stopping of the cooling fan according tothe temperature change inside the device. Further, as the measureagainst low temperature, when started up at a low temperature below apredetermined startup temperature, the CPU constituting the main unit ofthe electric device (server devices and the like) keeps the BIOSoperating state without executing the OS, and carries out a warm-upoperation. During the warm-up operation, the cooling fan is stopped.During the warm-up operation, the temperature inside the device risesdue to the heat emitted by the main unit of the device and, when itreaches the startup temperature, the CPU executes the OS, andsubsequently executes application programs.

[Patent Document 1] JP2004-185439 A

Because the electric device disclosed in Patent Document 1 utilizes theheat emitted by the main unit of the electric device to carry out thewarm-up operation, it does not need a heat source such as a heater andthe like as the measure against low temperature. However, the coolingfan for the measure against high temperature is stopped during thewarm-up operation. This is because it is conceivable that if the coolingfan is rotated during the warm-up operation, then the air inside thedevice (to be referred to as the inner air) warmed at last may beexchanged with the air outside the device (to be referred to as theouter air) so as to hinder the temperature rise inside the device.However, his phenomenon occurs when the outer air is lower intemperature than the inner air, but does not occur when the outer air ishigher in temperature than the inner air. On the contrary, if the outerair is hotter than the inner air, then it is possible to facilitatetemperature rise inside the electric device by introducing the outerair.

SUMMARY

Therefore, an exemplary object of the present invention is to provide anelectric device to solve the problem described hereinabove, that is, theproblem that the outer air is not effectively made use of at the time ofstartup in a low-temperature environment.

An aspect in accordance with the present invention provides an electricdevice having a casing with an air-inlet and an air-outlet, and a mainunit disposed inside the casing, the electric device including: a firsttemperature sensor for detecting the temperature inside the casing; asecond temperature sensor for detecting the temperature outside thecasing; an electric fan; and a control unit for rotating the electricfan at the time of the low-temperature startup such that the temperaturedetected by the first temperature sensor is lower than a preset firstthreshold value, while the temperature detected by the secondtemperature sensor is higher than the temperature detected by the firsttemperature sensor.

Further, another aspect in accordance with the present inventionprovides an activation method to be carried out by an electric devicehaving a casing with an air-inlet and an air-outlet, a main unitdisposed inside the casing, a first temperature sensor for detecting thetemperature inside the casing, a second temperature sensor for detectingthe temperature outside the casing, an electric fan, and a control unit,the activation method including: rotating the electric fan by thecontrol unit at the time of the low-temperature startup such that thetemperature detected by the first temperature sensor is lower than apreset first threshold value, while the temperature detected by thesecond temperature sensor is higher than the temperature detected by thefirst temperature sensor.

Because the present invention is configured in the above manner, it ispossible to facilitate temperature rise inside the electric device byeffectively making use of the outer air warmer than the inner air.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a first exemplary embodiment in accordancewith the present invention;

FIG. 2 is a block diagram of a second exemplary embodiment in accordancewith the present invention;

FIG. 3 is a block diagram of a third exemplary embodiment in accordancewith the present invention;

FIG. 4 is a block diagram of a fourth exemplary embodiment in accordancewith the present invention: and

FIG. 5 shows a control flow in the fourth exemplary embodiment inaccordance with the present invention.

EXEMPLARY EMBODIMENTS

Hereinbelow, referring to the accompanying drawings, exemplaryembodiments of the present invention will be explained in detail.

A First Exemplary Embodiment

Referring to FIG. 1, an electric device 100 in accordance with the firstexemplary embodiment of the present invention is composed of a main unit101, a control unit 102, a fan 103, temperature sensors 104 and 105, anda casing 106 for accommodating these components.

Mainly as a measure against high temperature for the casing 106, anair-inlet 107 for introducing the outer air into the casing and anair-outlet 108 for releasing the inner air out of the casing areprovided to be opposite to each other.

The main unit 101 is the portion governing main functions of theelectric device 100.

For example, if the electric device 100 is an IT device, then thecomputer constituting the IT device corresponds to the main unit 101.The main unit 101 is not limited to a computer, but may as well be abattery device such as a lithium battery and the like, or be configuredby other devices than computers and batteries.

The fan 103 is an electric fan provided mainly as a measure against hightemperature to disperse heat. However, in the first exemplaryembodiment, the fan 103 is also made use of as a measure against lowtemperature. When started by the control unit 102, the fan 103 rotatesin the direction of invoking an airflow from the air-inlet 107 towardthe air-outlet 108 through the inside of the casing.

The temperature sensor 104 serves to detect the temperature inside thecasing 106, that is, the inner air temperature. The temperature sensor105 serves to detect the temperature outside the casing 106, that is,the outer air temperature. Although FIG. 1 shows that the temperaturesensor 105 for detecting the outer air temperature is provided on theoutside of the casing 106 in the vicinity of the air-inlet 107, it mayas well be provided inside the casing 106 in the vicinity of theair-inlet 107 or air-outlet 108. The reason is that the vicinity of theair-inlet or air-outlet receives the influence of outer air.

The control unit 102 is electrically connected to the fan 103, thetemperature sensors 104 and 105, and the main unit 101 through signallines. The control unit 102 has a function to control the temperaturemeasuring by the temperature sensors 104 and 105, the starting andstopping of the fan 103, the starting and stopping of the main unit 10and the like.

Next, the operation of the first exemplary embodiment will be explained.

When the electric device 100 is started by pressing an unshown startbutton, etc., the control unit 102 determines whether or not the innerair temperature of the device detected by the temperature sensor 104 islower than a preset first threshold value. If the inner air temperatureis not lower than the first threshold value, then the control unit 102determines the low-temperature control to be unnecessary, andimmediately starts up the main unit 101. If the main unit 101 is acomputer including a CPU, for example, the control unit 102 starts upthe main unit 101 by causing the CPU to execute the OS.

On the other hand, if the inner air temperature is lower than the firstthreshold value, then the control unit 102 carries out thelow-temperature control. First, the control unit 102 determines whetheror not the outer air temperature detected by the temperature sensor 105is higher than the inner air temperature detected by the temperaturesensor 104. Next, if the outer air temperature is higher than the innerair temperature, then the control unit 102 rotates the fan 103. Byvirtue of introducing the outer air warmer than the inner air from theair-inlet 107 into the casing 106, the temperature of the main unit 101rises gradually. Thereafter, if either the temperature on thetemperature sensor 104 comes to be equal to or higher than the firstthreshold value or a predetermined condition is established such as acertain time elapses and the like, then the control unit 102 starts upthe main unit 101. Further, the control unit 102 adjusts the temperatureinside the device by controlling the starting and stopping of the fan103 according to the temperature change inside the device during theordinary operation of the electric device 100. For example, if thetemperature detected by the temperature sensor 104 is higher than asecond high-temperature threshold value equal to or higher than the Dratthreshold value, then the control unit 102 rotates the fan 103.

At the start time of the low-temperature control, the operation of thecontrol unit 102 may be arbitrary when the outer air temperature is nothigher than the inner air temperature. For example, if there is someother unit for raising the temperature of the main unit 101, then themain unit 101 may wait to be started until that unit raises thetemperature of the main unit 101 to higher than the first thresholdvalue. Alternatively, if there is no other unit like that, then thecontrol unit 102 may either not start up the main unit 101 or venture tostart up the main unit 101 even at a low temperature.

In this manner, according to the first exemplary embodiment, at the timeof starting up the device at low temperatures, it is possible tofacilitate temperature rise inside the electric device by utilizing theouter air with a higher temperature than the inner air.

Further, according to the first exemplary embodiment, it is possible tomake use of the fan 103 utilized originally in heat dispersion for themeasure against low temperatures without any physical modification.

A Second Exemplary Embodiment

Referring to FIG. 2, compared with the electric device 100 in accordancewith the first exemplary embodiment shown in FIG. 1, an electric device200 in accordance with a second exemplary embodiment of the presentinvention is different in the aspect of having a control unit 202, a fan203, and a temperature sensor 205 instead of the control unit 102, thefan 103, and the temperature sensor 105.

The temperature sensor 205 serves to detect the outer air temperature inthe vicinity of the air-outlet 108 of the casing 106. Although FIG. 2shows that the temperature sensor 205 is provided on the outside of thecasing 106, it may as well be provided inside the casing 106 in thevicinity of the air-outlet 108. The reason is that the vicinity of theair-outlet 108 receives the influence of outer air.

The fan 203 is an electric fan provided mainly as a measure against hightemperature to disperse heat. However, in the second exemplaryembodiment, the fan 203 is also made use of as a measure against lowtemperature. The fan 203 can rotate in the direction of invoking anairflow from the air-inlet 107 toward the air-outlet 108 through theinside of the casing as well as in the opposite direction. Hereinbelow,the former will be referred to as the positive rotation, whereas thelatter will be referred to as the negative or inverse rotation.

The control unit 202 is electrically connected to the fan 203, thetemperature sensors 104 and 205, and the main unit 101 through signallines. The control unit 202 has a function to control the temperaturemeasuring by the temperature sensors 104 and 205, the starting, stoppingand rotation direction of the fan 203, the starting and stopping of themain unit 101, and the like.

Next, the operation of the second exemplary embodiment will be explainedmainly with a focus on the different aspects from the first exemplaryembodiment.

When the electric device 200 is started by pressing an unshown startbutton, etc., the control unit 202 determines whether or not the innerair temperature of the device detected by the temperature sensor 104 islower than a preset first threshold value. If the inner air temperatureis not lower than the first threshold value, then the control unit 202determines the low-temperature control to be unnecessary, andimmediately starts up the main unit 101.

On the other hand, if the inner air temperature is lower than the firstthreshold value, then the control unit 202 carries out thelow-temperature control. First, the control unit 202 determines whetheror not the outer air temperature detected by the temperature sensor 205is higher than the inner air temperature detected by the temperaturesensor 104. Next, if the outer air temperature is higher than the innerair temperature, then the control unit 202 inversely rotates the fan203. By virtue of introducing the outer air warmer than the inner airfrom the air-outlet 108 into the casing 106, the temperature of the mainunit 101 rises gradually. Thereafter, if either the temperature on thetemperature sensor 104 comes to be equal to or higher than the firstthreshold value or a predetermined condition is established such as acertain time elapses and the like, then the control unit 202 starts upthe main unit 101. Further, the control unit 202 adjusts the temperatureinside the device by controlling the starting and stopping of thepositive rotation of the fan 203 according to the temperature changeinside the device during the ordinary operation of the electric device200. For example, if the temperature detected by the temperature sensor104 is higher than a second high-temperature threshold value equal to orhigher than the first threshold value, then the control unit 202positively rotates the fan 203.

At the start time of the low-temperature control, in the same manner asthe control unit 102 in the first exemplary embodiment, the operation ofthe control unit 202 may be arbitrary when the outer air temperature isnot higher than the inner air temperature.

In this manner, according to the second exemplary embodiment, at thetime of starting up the device at low temperatures, it is possible tofacilitate temperature rise inside the electric device by utilizing theouter air with a higher temperature than the inner air. In particular,the second exemplary embodiment exerts its effect especially on the caseof utilizing a plurality of electric device 200 in the same place. Thereason is as follows.

In cases of setting up the electric device 200 together with othersimilar electric devices, their air-outlets generally face in the samedirection. For example, in the case of aligning a plurality of electricdevices in a row along the wall surface in a room, their air-outletsoften face the wall side. Therefore, when some of the electric devicesare in operation, because the exhaust heat of those electric devices inoperation is released to the air-outlet side, the temperature on theair-outlet side tends to become higher in comparison with the air-inletside. In the second exemplary embodiment, because of inversely rotatingthe fan 203, it is possible to warm up the main unit 101 by utilizingthe outer air on the air-outlet side with a higher temperature than theair-inlet side.

A Third Exemplary Embodiment

Referring to FIG. 3, compared with the electric device 200 in accordancewith the second exemplary embodiment shown in FIG. 2, an electric device300 in accordance with a third exemplary embodiment of the presentinvention is different in the aspect of adding a temperature sensor 305,and having a control unit 302 instead of the control unit 202.

Similar to the temperature sensor 105 of the first exemplary embodimentin FIG. 1, the temperature sensor 305 serves to detect the outer airtemperature in the vicinity of the air-inlet 107 of the casing 106.Although FIG. 3 shows that the temperature sensor 305 is provided on theoutside of the casing 106, it may as well be provided inside the casing106 in the vicinity of the air-inlet 107.

The control unit 302 is electrically connected to the fan 203, thetemperature sensors 104, 205 and 305, and the main unit 101 throughsignal lines. The control unit 302 has a function to control thetemperature measuring by the temperature sensors 104, 205 and 305, thestarting, stopping and rotation direction of the fan 203, the startingand stopping of the main unit 101, and the like.

Next, the operation of the third exemplary embodiment will be explainedmainly with a focus on the different aspects from the first and secondexemplary embodiments.

When the electric device 300 is started by pressing an unshown startbutton, etc., the control unit 302 determines whether or not the innerair temperature of the device detected by the temperature sensor 104 islower than a preset first threshold value. If the inner air temperatureis not lower than the first threshold value, then the control unit 302determines the low-temperature control to be unnecessary, andimmediately starts up the main unit 101.

On the other hand, if the inner air temperature is lower than the firstthreshold value, then the control unit 302 carries out thelow-temperature control. First, the control unit 302 compares the outerair temperature on the air-outlet side detected by the temperaturesensor 205 with the outer air temperature on the air-inlet side detectedby the temperature sensor 305, and selects the higher one. Next, thecontrol unit 302 determines whether or not the selected outer airtemperature is higher than the inner air temperature of the devicedetected by the temperature sensor 104. Then, if the selected outer airtemperature is higher than the inner air temperature, then the controlunit 302 rotates the fan 203 to introduce the outer air into the casing106, warming up the main unit 101 with the outer air warmer than theinner air. At this time, if the outer air on the air-outlet side isselected, then the control unit 302 inversely rotates the fan 203 tointroduce the outer air from the air-outlet 108 into the casing 106. Onthe other hand, if the outer air on the air-inlet side is selected, thenthe control unit 302 positively rotates the fan 203 to introduce theouter air from the air-inlet 107 into the casing 106. Thereafter, ifeither the temperature on the temperature sensor 104 comes to be equalto or higher than the first threshold value or a predetermined conditionis established such as a certain time elapses and the like, then thecontrol unit 302 starts up the main unit 101. Further, the control unit302 adjusts the temperature inside the device by controlling thestarting and stopping of the positive rotation of the fan 203 accordingto the temperature change inside the device during the ordinaryoperation of the electric device 300.

At the start time of the low-temperature control, in the same manner asthe control units 102 and 202 in the first and second exemplaryembodiments, the operation of the control unit 302 may be arbitrary whenthe selected outer air temperature is not higher than the inner airtemperature.

In this manner, according to the third exemplary embodiment, at the timeof starting up the device at low temperatures, it is possible tofacilitate temperature rise inside the electric device by utilizing theouter air with a higher temperature than the inner air. In particular,the third exemplary embodiment is capable of selectively introducing theouter air with a higher temperature from the air-inlet side and theair-outlet side.

A Fourth Exemplary Embodiment Outline

One of the characteristics of the fourth exemplary embodiment lies ingradually raising the temperature inside a computer being activated ifthe temperature inside the computer is lower than the guaranteedoperating temperature, and starting the OS after controlling thetemperature into a safe state as the operating temperature for thecomputer. Further, another characteristic of the fourth exemplaryembodiment is that a higher versatility is available because it ispossible to realize it almost without changing the structure of anordinary computer.

Explanation of the Configuration

Referring to FIG. 4, a computer 400 in accordance with the fourthexemplary embodiment is constituted by an HDD 402 (Hard Disk Drive), atemperature sensor 402-a installed in the vicinity of the HDD, a fan 403capable of positive and inverse rotations, a CPU 404, a temperaturesensor 404-a installed in the vicinity of the CPU, a memory 405, an IO406 (Input Output unit), a temperature sensor 406-a installed in thevicinity of the 10, a management unit 407, a power supply 408, and acasing 401 for accommodating the above components. The casing 401 isprovided with an air-inlet (not shown) on the front side, and anair-outlet (not shown) on the back side. Although FIG. 4 shows two CPUs,five fans, four HDDs, one memory, one 10, and one power supply, thenumber of these components is arbitrary. Further, the arrangement ofeach component in the casing 401 is not limited to that shown in thefigure either.

The management unit 407 corresponds to the control units 102, 202 and302 in the first to third exemplary embodiments, respectively. Themanagement unit 407 is electrically connected to the other componentssuch as the temperature sensor 402-a, temperature sensor 404-a,temperature sensor 406-a, fan 403, CPU 404, CPU 404, and the likethrough unshown signal lines. The management unit 407 has amicroprocessor (not shown), and is programmed to carry out the controlflow shown in FIG. 5.

Explanation of the Operation

When a user and the like issues an instruction to start up the computer400 (step S1), the management unit 407 confirms the temperature detectedby each of the temperature sensors 402-a, 404-a and 406-a installedinside the computer (step S2). Then, the management unit 407 determineswhether or not the temperature detected by any one of the temperaturesensors is lower than the guaranteed operating temperature prestored inthe memory of the management unit 407 (step S3).

If the temperature detected by any one of the temperature sensors islower than the guaranteed operating temperature (Yes at step S3), thenthe management unit 407 starts the low-temperature control (step S4).Under the low-temperature control, first, the management unit 407operates the CPU (processor) on a clock with a lower frequency thanusual to start a self-test operation (a startup diagnostic programimplemented generally in starting the computer; step S5).

In addition, the management unit 407 determines whether or not thetemperature of the computer on the air-outlet side (the temperaturedetected by the temperature sensor 406-a) is higher than the temperatureof the computer on the central or air-inlet side (the temperaturedetected by the temperature sensor 404-a or temperature sensor 402-a;step S7). Then, if the temperature on the air-outlet side is higher thanthe temperature on the central or air-inlet side (Yes at step S7), thenthe management unit 407 inversely rotates the fan 403 to take in theouter air (step S8). By virtue of this, the air on the air-outlet sideis taken into the computer. Since a computer generally intakes air fromthe front and discharges air at the back, when other devices inoperation are mounted on the rack (cabinet) on which a starting-upcomputer is also mounted, the exhaust heat is released to the back side(the air-outlet side). In this manner, the fourth exemplary embodimentmakes use of the possibility of a high temperature on the air-outletside.

As the computer completes the self-test (step S6), the management unit407 confirms again the temperature detected by each temperature sensor(step S2), and compares the same with the guaranteed operatingtemperature (step S3). If the comparison result shows it still lowerthan the guaranteed operating temperature as before, then the self-testis carried out over again (step S5). By virtue of this, with the heatemitted by the components installed in the computer, the temperature ofthe entire computer rises gradually.

If the temperature detected by each temperature sensor is higher thanthe guaranteed operating temperature (No at step S3), then themanagement unit 407 shifts the process to the ordinary OS startup. Atthe time, if the fan 403 is set at the inverse rotation in the controlprocess at low temperatures, then the management unit 407 returns thesetting to the positive rotation (step S9). Further, if the clockfrequency of the CPU is at the low level, then the management unit 407changes it to the ordinary high clock frequency (step S10). Then, themanagement unit 407 activates the OS on the CPU and, subsequently,activates the application programs (step S11).

Explanation of the Effect

According to the fourth exemplary embodiment, it is possible tofacilitate temperature rise of the device at low temperatures in a safermanner to carry out the process up to the OS activation by the computeritself without changing the computer structure. Because it is notnecessary to provide special equipment such as heaters and the like,extra equipment cost does not arise.

Conventionally, it is common to let a computer operate successively.However, due to the recent-year movements of the ecological activities,CO₂ reduction and the like, the environment for operating and installingcomputers is experiencing a great change such as shutting down computersat night, introducing the outer air throughout the year, leaving outair-conditioning equipment, and the like. Conceivably, such trend willpick up even more in the days to come, and the need to operate computersfrom the state of low temperatures will increase more and more.According to the fourth exemplary embodiment, in answer to such need, itis possible to operate computers safely in a low-temperature environmentand provide a low-cost method for realizing the purpose.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the claims. Further, the present invention can realize thenecessary functions not only on hardware as a matter of course, but withcomputers and a program as well. The program is provided in the form ofbeing recorded in a computer-readable recording medium such as magneticdisks, semiconductor memories, and the like, and is read out by acomputer at the time of starting the computer and the like to make thecomputer function as the control unit 102, 202, or 302 in each of theaforementioned exemplary embodiments by controlling the operation of thecomputer.

The whole or part of the exemplary embodiment disclosed above can bedescribed as, but not limited to, the following supplementary notes.

(Supplementary Note 1)

An electric device having a casing with an air-inlet and an air-outlet,and a main unit disposed inside the casing, the electric devicecomprising:

a first temperature sensor for detecting the temperature inside thecasing;

a second temperature sensor for detecting the temperature outside thecasing;

an electric fan; and

a control unit for rotating the electric fan at the time of thelow-temperature startup such that the temperature detected by the firsttemperature sensor is lower than a preset first threshold value, whilethe temperature detected by the second temperature sensor is higher thanthe temperature detected by the first temperature sensor.

(Supplementary Note 2)

The electric device according to Supplementary Note 1, wherein thecontrol unit rotates the electric fan at the time of the low-temperaturestartup in the direction of invoking an airflow from the air-outletthrough the inside of the casing toward the air-inlet.

(Supplementary Note 3)

The electric device according to Supplementary Note 2, wherein thesecond temperature sensor is installed in the vicinity of theair-outlet.

(Supplementary Note 4)

The electric device according to Supplementary Note 1, wherein thesecond temperature sensor has a third temperature sensor installed inthe vicinity of the air-inlet and a fourth temperature sensor installedin the vicinity of the air-outlet; and the control unit selects thetemperature sensor detecting a higher temperature at the time of thelow-temperature startup between the third temperature sensor and thefourth temperature sensor and, when the temperature detected by theselected temperature sensor is higher than the temperature detected bythe first temperature sensor, rotates the electric fan in the directionof invoking an airflow from the air-inlet through the inside of thecasing toward the air-outlet if the selected temperature sensor is thethird temperature sensor, but rotates the electric fan in the directionof invoking an airflow from the air-outlet through the inside of thecasing toward the air-inlet if the selected temperature sensor is thefourth temperature sensor.

(Supplementary Note 5)

The electric device according to Supplementary Note 1, wherein thecontrol unit rotates the electric fan at the time of the low-temperaturestartup in the direction of invoking an airflow from the air-inletthrough the inside of the casing toward the air-outlet.

(Supplementary Note 6)

The electric device according to Supplementary Note 5, wherein thesecond temperature sensor is installed in the vicinity of the air-inlet.

(Supplementary Note 7)

The electric device according to any of Supplementary Notes 1 to 6,wherein the control unit rotates the electric fan in the direction ofinvoking an airflow from the air-inlet through the inside of the casingtoward the air-outlet after the temperature detected by the firsttemperature sensor reaches a temperature higher than the first thresholdvalue.

(Supplementary Note 8)

The electric device according to any of Supplementary Notes 1 to 7,wherein the main unit has a CPU; and the control unit makes the CPUoperate on a clock with a lower frequency than usual until thetemperature detected by the first temperature sensor exceeds the firstthreshold value.

(Supplementary Note 9)

The electric device according to Supplementary Note 8, wherein thecontrol unit causes the CPU made to operate on the clock with the lowerfrequency to carry out a self-test.

(Supplementary Note 10)

An activation method to be carried out by an electric device having acasing with an air-inlet and an air-outlet, a main unit disposed insidethe casing, a first temperature sensor for detecting the temperatureinside the casing, a second temperature sensor for detecting thetemperature outside the casing, an electric fan, and a control unit, theactivation method comprising:

rotating the electric fan by the control unit at the time of thelow-temperature startup such that the temperature detected by the firsttemperature sensor is lower than a preset first threshold value, whilethe temperature detected by the second temperature sensor is higher thanthe temperature detected by the first temperature sensor.

(Supplementary Note 11)

The activation method according to Supplementary Note 10, wherein thecontrol unit rotates the electric fan at the time of the low-temperaturestartup in the direction of invoking an airflow from the air-outletthrough the inside of the casing toward the air-inlet.

(Supplementary Note 12)

12. The activation method according to Supplementary Note 11, whereinthe second temperature sensor detects the temperature in the vicinity ofthe air-outlet.

(Supplementary Note 13)

The activation method according to Supplementary Note 10, wherein thesecond temperature sensor has a third temperature sensor installed inthe vicinity of the air-inlet and a fourth temperature sensor installedin the vicinity of the air-outlet; and the control unit selects thetemperature sensor detecting a higher temperature at the time of thelow-temperature startup between the third temperature sensor and thefourth temperature sensor and, when the temperature detected by theselected temperature sensor is higher than the temperature detected bythe first temperature sensor, rotates the electric fan in the directionof invoking an airflow from the air-inlet through the inside of thecasing toward the air-outlet if the selected temperature sensor is thethird temperature sensor, but rotates the electric fan in the directionof invoking an airflow from the air-outlet through the inside of thecasing toward the air-inlet if the selected temperature sensor is thefourth temperature sensor.

(Supplementary Note 14)

The activation method according to Supplementary Note 10, wherein thecontrol unit rotates the electric fan at the time of the low-temperaturestartup in the direction of invoking an airflow from the air-inletthrough the inside of the casing toward the air-outlet.

(Supplementary Note 15)

The activation method according to Supplementary Note 14, wherein thesecond temperature sensor detects the temperature in the vicinity of theair-inlet.

(Supplementary Note 16)

The activation method according to any of Supplementary Notes 10 to 15,wherein the control unit rotates the electric fan in the direction ofinvoking an airflow from the air-inlet through the inside of the casingtoward the air-outlet after the temperature detected by the firsttemperature sensor reaches a temperature higher than the first thresholdvalue.

(Supplementary Note 17)

The activation method according to any of Supplementary Notes 10 to 16,wherein the main unit has a CPU; and the control unit makes the CPUoperate on a clock with a lower frequency than usual until thetemperature detected by the first temperature sensor exceeds the firstthreshold value.

(Supplementary Note 18)

The activation method according to Supplementary Note 17, wherein thecontrol unit causes the CPU made to operate on the clock with the lowerfrequency to carry out a self-test.

(Supplementary Note 19)

An electric device having a casing with an air-inlet and an air-outlet,and a main unit disposed inside the casing, the electric devicecomprising:

a first temperature sensor for detecting the temperature inside thecasing;

a second temperature sensor for detecting the temperature outside thecasing; an electric fan; and

a control means for rotating the electric fan at the time of thelow-temperature startup such that the temperature detected by the firsttemperature sensor is lower than a preset first threshold value, whilethe temperature detected by the second temperature sensor is higher thanthe temperature detected by the first temperature sensor.

(Supplementary Note 20)

A computer-readable medium storing a program comprising instructions forcausing a computer of an electric device having a casing with anair-inlet and an air-outlet, a main unit disposed inside the casing, afirst temperature sensor for detecting the temperature inside thecasing, a second temperature sensor for detecting the temperatureoutside the casing, an electric fan, and the computer to carry out aprocess of rotating the electric fan at the time of the low-temperaturestartup such that the temperature detected by the first temperaturesensor is lower than a preset first threshold value, while thetemperature detected by the second temperature sensor is higher than thetemperature detected by the first temperature sensor.

(Supplementary Note 21)

A computer program comprising instructions which cause a computer of anelectric device having a casing with an air-inlet and an air-outlet, amain unit disposed inside the casing, a first temperature sensor fordetecting the temperature inside the casing, a second temperature sensorfor detecting the temperature outside the casing, an electric fan, andthe computer to carry out a process of rotating the electric fan at thetime of the low-temperature such that the temperature detected by thefirst temperature sensor is lower than a preset first threshold value,while the temperature detected by the second temperature sensor ishigher than the temperature detected by the first temperature sensor.

The invention claimed is:
 1. An electric device having a casing with anair-inlet and an air-outlet, and a central processing unit (CPU)disposed inside the casing, the electric device comprising: a firsttemperature sensor for detecting the temperature inside the casing; asecond temperature sensor for detecting the temperature outside thecasing; an electric fan; and a control unit for rotating the electricfan at a time of a low-temperature startup in which the temperaturedetected by the first temperature sensor is lower than a preset firstthreshold value, and the temperature detected by the second temperaturesensor is higher than the temperature detected by the first temperaturesensor, wherein the electric fan, the CPU, and the air-outlet arearranged in the order of the electric fan, the CPU, and the air-outlet;wherein the second temperature sensor comprises a third temperaturesensor installed at the air-inlet and a fourth temperature sensorinstalled at the air-outlet; and wherein the control unit selects thetemperature sensor detecting a higher temperature at the time of thelow-temperature startup between the third temperature sensor and thefourth temperature sensor and, when the temperature detected by theselected temperature sensor is higher than the temperature detected bythe first temperature sensor, rotates the electric fan in the directionof invoking an airflow from the air-inlet through the inside of thecasing toward the air-outlet if the selected temperature sensor is thethird temperature sensor, but rotates the electric fan in the directionof invoking an airflow from the air-outlet through the inside of thecasing toward the air-inlet if the selected temperature sensor is thefourth temperature sensor.
 2. The electric device according to claim 1,wherein the control unit rotates the electric fan at the time of thelow-temperature startup in the direction of invoking an airflow from theair-outlet through the inside of the casing toward the air-inlet.
 3. Theelectric device according to claim 2, wherein the second temperaturesensor is installed at the air-outlet.
 4. The electric device accordingto claim 1, wherein the control unit rotates the electric fan at thetime of the low-temperature startup in the direction of invoking anairflow from the air-inlet through the inside of the casing toward theair-outlet.
 5. The electric device according to claim 4, wherein thesecond temperature sensor is installed at the air-inlet.
 6. The electricdevice according to claim 1, wherein the control unit rotates theelectric fan in the direction of invoking an airflow from the air-inletthrough the inside of the casing toward the air-outlet after thetemperature detected by the first temperature sensor reaches atemperature higher than the first threshold value.
 7. The electricdevice according to claim 1, wherein the the control unit makes the CPUoperate on a clock having a lower frequency than usual until thetemperature detected by the first temperature sensor exceeds the firstthreshold value.
 8. The electric device according to claim 7, whereinthe control unit causes the CPU made to operate on the clock having thelower frequency to carry out a self-test.
 9. The electric deviceaccording to claim 1, wherein the control unit is housed inside thecasing.
 10. The electric device according to claim 1, wherein theelectric fan is housed inside the casing.
 11. The electric deviceaccording to claim 1, wherein the central processing unit (CPU) ishoused inside the casing and adjacent to the first temperature sensor.12. The electric device according to claim 1, wherein the electricdevice further comprising an electric component; the electric componentis housed inside the casing; and the electric component, the electricfan, and the CPU are arranged in the order of the electric component,the electric fan, and the CPU.
 13. The electric device according toclaim 1, wherein the air-inlet is on the front side of the casing andthe air-outlet is on the back side of the casing.
 14. An activationmethod to be carried out by an electric device having a casing with anair-inlet and an air-outlet, a central processing unit (CPU) disposedinside the casing, a first temperature sensor for detecting atemperature inside the casing, a second temperature sensor for detectinga temperature outside the casing, an electric fan, and a control unit,the activation method comprising: rotating the electric fan by thecontrol unit at a time of a low-temperature startup in which thetemperature detected by the first temperature sensor is lower than apreset first threshold value, and the temperature detected by the secondtemperature sensor is higher than the temperature detected by the firsttemperature sensor, wherein the electric fan, the CPU, and theair-outlet are arranged in the order of the electric fan, the CPU, andthe air-outlet; wherein the second temperature sensor comprises a thirdtemperature sensor installed at the air-inlet and a fourth temperaturesensor installed at the air-outlet; and wherein the control unit selectsthe temperature sensor detecting a higher temperature at the time of thelow-temperature startup between the third temperature sensor and thefourth temperature sensor and, when the temperature detected by theselected temperature sensor is higher than the temperature detected bythe first temperature sensor, rotates the electric fan in the directionof invoking an airflow from the air-inlet through the inside of thecasing toward the air-outlet if the selected temperature sensor is thethird temperature sensor, but rotates the electric fan in the directionof invoking an airflow from the air-outlet through the inside of thecasing toward the air-inlet if the selected temperature sensor is thefourth temperature sensor.
 15. The activation method according to claim14, wherein the control unit rotates the electric fan at the time of thelow-temperature startup in the direction of invoking an airflow from theair-outlet through the inside of the casing toward the air-inlet. 16.The activation method according to claim 15, wherein the secondtemperature sensor detects the temperature at the air-outlet.
 17. Theactivation method according to claim 14, wherein the control unitrotates the electric fan at the time of the low-temperature startup inthe direction of invoking an airflow from the air-inlet through theinside of the casing toward the air-outlet.
 18. The activation methodaccording to claim 17, wherein the second temperature sensor detects thetemperature at the air-inlet.
 19. The activation method according toclaim 14, wherein the control unit rotates the electric fan in thedirection of invoking an airflow from the air-inlet through the insideof the casing toward the air-outlet after the temperature detected bythe first temperature sensor reaches a temperature higher than the firstthreshold value.
 20. The activation method according to claim 14,wherein the control unit makes the CPU operate on a clock having a lowerfrequency than usual until the temperature detected by the firsttemperature sensor exceeds the first threshold value.
 21. The activationmethod according to claim 20, wherein the control unit causes the CPUmade to operate on the clock having the lower frequency to carry out aself-test.
 22. A non-transitory computer-readable medium storing aprogram comprising instructions for causing a computer of an electricdevice having a casing with an air-inlet and an air-outlet, a centralprocessing unit (CPU) disposed inside the casing, a first temperaturesensor for detecting a temperature inside the casing, a secondtemperature sensor for detecting a temperature outside the casing, anelectric fan, and the computer, to perform an activation methodcomprising: rotating the electric fan at a time of a low-temperaturestartup such that the temperature detected by the first temperaturesensor is lower than a preset first threshold value, while thetemperature detected by the second temperature sensor is higher than thetemperature detected by the first temperature sensor, wherein theelectric fan, the CPU, and the air-outlet are arranged in the order ofthe electric fan, the CPU, and the air-outlet; wherein the secondtemperature sensor comprises a third temperature sensor installed at theair-inlet and a fourth temperature sensor installed at the air-outlet;and wherein the control unit selects the temperature sensor detecting ahigher temperature at the time of the low-temperature startup betweenthe third temperature sensor and the fourth temperature sensor and, whenthe temperature detected by the selected temperature sensor is higherthan the temperature detected by the first temperature sensor, rotatesthe electric fan in the direction of invoking an airflow from theair-inlet through the inside of the casing toward the air-outlet if theselected temperature sensor is the third temperature sensor, but rotatesthe electric fan in the direction of invoking an airflow from theair-outlet through the inside of the casing toward the air-inlet if theselected temperature sensor is the fourth temperature sensor.